Skyshine vs Direct Dose in MCNP5

AI Thread Summary
The discussion centers on defining and calculating the skyshine dose in MCNP, particularly in scenarios involving a source and shielding. Skyshine refers to radiation that scatters off the atmosphere and reaches a dose point beyond any radiological shielding. Participants suggest using an importance factor of 0 for faster calculations, noting that this approach yields results comparable to more complex methods. The conversation also touches on the challenges of separating skyshine contributions when the source region is large, such as a building. Ultimately, the participants agree on the significance of understanding skyshine in radiation safety assessments.
Will_007
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how to calculate skyshine dose with mcnp?
Hello - what is an accepted definition of the skyshinne dose in MCNP and how would you calculate this? If you have a source and a shield a few meters away between the dose point, the contribution that goes around the shield would be skyshine....but..what if you have a big source region (e.g., a building) and your dose point is a mile away - how would you separate skyshine component?

Thanks
 
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Hi, you can consider an importance (imp:p 0) 0, in the primary barrier
 
PSRB191921 said:
Hi, you can consider an importance (imp:p 0) 0, in the primary barrier
Hey - yeah. This was my ultimate choice. Initially I put in a slab with really high fictitious density in the middle of my shield (to allow stuff to scatter back and around to the dose location), but ran a test case and imp=0 was way faster and almost identical results.

if there is no shield (other than air), and source is 50 yards away from the dose point, what does skyshine mean to you?
 
"Skyshine" is a radiation scattered by sky air, outside the radiological
shielding.
In the first figure (geometry definition) in the second results with MCNP (reference Radiation Problems : From Analytical to Monte-Carlo Solutions ) :
skyshine.jpg
skyshineMCNP.jpg
 
thanks
 
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